doc: Update gcloud command for ADC (googleapis#406)

sai-sunder-s · parthea · web-flow · commit 7472e6d10e8e · 2022-08-09T21:56:45.000-04:00
ADC login command for gcloud is `gcloud auth application-default auth login`

Co-authored-by: Anthonios Partheniou &lt;partheniou@google.com&gt;
diff --git a/docs/auth.rst b/docs/auth.rst
@@ -165,7 +165,7 @@ possible to call Google Cloud APIs with a user account via
     getting started with the ``google-cloud-*`` library.
 
 The simplest way to use credentials from a user account is via
-Application Default Credentials using ``gcloud auth login``
+Application Default Credentials using ``gcloud auth application-default login``
 (as mentioned above) and :func:`google.auth.default`:
 
 .. code:: python
